Greywater (
also spelled graywater) or
sullage is all
wastewater generated in households or office buildings from streams without fecal contamination, i.e. all streams except for the wastewater from toilets. Sources of greywater include, e.g.
sinks,
showers,
baths, clothes
washing machines or dish washers. As greywater contains fewer
pathogens than domestic wastewater, it is generally safer to handle and easier to treat and reuse onsite for
toilet flushing, landscape or crop
irrigation, and other non-potable uses. However, the use of non-toxic and low-sodium soap and personal care products is recommended to protect vegetation when reusing greywater for irrigation purposes. The application of greywater reuse in
urban water systems provides substantial benefits for both the
water supply subsystem by reducing the demand for fresh
clean water as well as the wastewater subsystems by reducing the amount of wastewater required to be conveyed and treated.